1. Field of the Invention
The present invention relates to a method for producing a substrate having irregular concavities and convexities used for production of an organic electro-luminescent element and the like and a method for producing an organic EL using the same.
2. Description of the Related Art
As a self-luminescent display element, there has been known an organic electro-luminescent element (also referred to as an organic light-emitting diode. Hereinbelow, referred to as an “organic EL element”). As compared with a liquid crystal element, the organic EL element has high visibility and does not need a backlight, and thus it is possible to reduce the weight thereof. For this reason, research and development of the organic EL element as the display element for the next generation has been actively carried out.
In the organic EL element, a hole injected from a hole injecting layer and electron injected from an electron injecting layer are carried to a light emitting layer respectively, then the hole and the electron are recombined on an organic molecule in the light emitting layer to excite the organic molecule, and thereby light emission occurs. Therefore, in a case that the organic EL element is used as a display device, the light from the light emitting layer is required to be efficiently extracted from the surface of the organic EL element. In order to meet this demand, Japanese Patent Application Laid-open No. 2006-236748 and the like disclose that a diffraction-grating substrate is provided on a light extraction surface of the organic EL element.
The applicant of the present invention discloses the following method in International Publication No. WO2011/007878A1. That is, a solution obtained by dissolving a block copolymer satisfying a predetermined condition into a solvent is applied on a base member, and drying is performed to form a micro phase separation structure of the block copolymer, thereby obtaining a master block (metal substrate) in which a minute or fine and irregular concavity and convexity pattern is formed. According to this method, it is possible to obtain the master block used for the nanoimprint and the like by using a self-organizing phenomenon of the block copolymer. A mixture of a silicone-based polymer and a curing agent is dripped onto the obtained master block and then cured to obtain a transferred pattern. Then, a glass substrate to which a curable resin has been applied is pressed against the transferred pattern and the curable resin is cured by irradiation with ultraviolet rays. In this way, a diffraction grating in which the transferred pattern is duplicated is manufactured. It has been confirmed that an organic EL element obtained by stacking a transparent electrode, an organic layer, and a metal electrode on the diffraction grating has sufficiently high light emission efficiency, sufficiently high level of external extraction efficiency, sufficiently low wavelength-dependence of light emission, sufficiently low directivity of light emission, and sufficiently high power efficiency.
It is desired that even the organic EL element in which the diffraction grating produced in International Publication No. WO2011/007878A1 as described above is used emits light at a uniform luminance from the entire display surface(s) in a case that the organic EL element is used as the display device and/or the illumination device of a cellular or mobile phone, a television screen, and the like. Thus, it is necessary to confirm whether or not the irradiation or emission from the organic EL element is uniform, that is, whether unevenness of luminance is within an acceptable range, after completion of the organic EL element. In a case that the unevenness of luminance of the completed organic EL element is judged to be beyond the acceptable range, the organic EL element is determined to be a unsatisfactory or defective product, and a step for stacking many layers on the diffraction grating as described above goes to waste. Especially, stacking of the transparent electrode, the organic layer, the metal electrode, and the like is a complex or time-consuming process requiring a high production cost. Therefore, it is strongly desired that the number of such the unsatisfactory or defective products is reduced to improve the yield rate, and thereby reducing the waste of the material and the production cost.
In view of the above, an object of the present invention is to provide a method for producing an organic EL element which includes a diffraction-grating substrate having an irregular concave and convex surface with a high throughput. Further, another object of the present invention is to provide a method for producing a substrate having an irregular concave and convex surface which is used as an optical component, the method including a step for evaluating unevenness of luminance of the substrate.